1. Field of Invention
The present invention is directed to a device for holding, especially sealing support of an optical element, especially a last optical element of an immersion objective that comes into contact with a liquid, preferably for holding of an optical lens. The device has at least one holding element for mounting the optical element and at least one sealing element for sealing contact with at least one part of the optical element and/or the holding element. Further, the invention refers to a method for the operation of such a device.
2. Discussion of Related Art
In objectives, optical elements, like optical lenses, are held in a mount, wherein usually sealing compounds, such as adhesives and the like are used so that, for example, dirt or other foreign particles may be prevented from penetrating into the space between optical element and mount and thus into the objective.
Such sealing compounds, like adhesives, but also other joining techniques that are used for connecting optical element and mount possess the disadvantage that through different thermal expansion of the components involved, through relaxation of stresses from the joining process, through swelling or shrinking of participating components, through chemical reactions, such as postcuring, embrittling etc. especially over the service life of the objective, different mechanical properties, such as holding and sealing forces are present. However, these also cause variation in the optical characteristics of the optical element through elastic deformation of the optical element. This is especially troublesome in the case of very precise objectives, for example projection objectives in microlithography.
Especially in the case of immersion objectives, whose last optical element, for example in the form of an optical lens or a transparent protective element, is in contact with an immersion liquid, such problems regarding undesirable introduction of mechanical stresses are caused by adhesive and/or sealing compounds that are used for sealing between the optical element and a surrounding mount, which is flange-mounted in the objective. Additionally, the sealing and/or adhesive compounds can lead to problems with aging effects that, in turn, can lead to stress being introduced into the held and sealed lens element. Additionally, adverse chemical reactions may occur between the immersion liquid and the sealing and/or adhesive compounds.